Comparison of different sorbent materials for on-line solid-phase extraction with liquid chromatography-atmospheric pressure chemical ionization massspectrometry of phenols

On-line solid-phase extraction (SPE) was interfaced to liquid chromatograph y with atmospheric pressure chemical ionization mass spectrometry (HPLC-APC I-MS) for the determination of US Environmental Protection Agency (EPA) phe nols. The system, allowing fully automated operation, was used to evaluate different SPE cartridge materials and dimensions. Six different SPE materia ls (C-18 HD, Polymer Labs PLRP-s, Hamilton PRP-1, Hysphere GP, Hysphere SH and Waters Oasis) were tested. Criteria for their comparison were first the recovery for the different phenols and its reproducibility, but also chrom atographically relevant items like peakshape in the on-line elution mode. H igh recoveries and good relative standard deviations were obtained particul arly for the newer, strongly retaining SPE materials that have become comme rcially available recently (the Hysphere materials and Waters Oasis) compar ed to the well known silica-based and weaker polymeric adsorbents like PLRP -s and PRP-1. These advantages are, however, traded in for good chromatogra phic peahshape, since the stronger adsorbents give rise to notable peak bro adening in on-line elution. This is particularly true when using APCI-MS de tection which on the one hand offers excellent selectivity and sensitivity, but imposes additional restrictions on the mobile phase composition in ord er not to suppress the response significantly. The influence of these param eters on the on-line-SPE-HPLC-MS determination of EPA phenols is discussed and present limitations are pointed out. (C) 2000 Elsevier Science B.V. All rights reserved.